1. Field of the Invention
The present invention relates to a control system/method for controlling range shifting in a compound transmission having a lever-shifted main section and a range section shifted by a range section actuator selectively positioning a synchronized double-acting positive clutch. In particular, the present invention relates to controlling range shifting in a lever-shifted, partially automated vehicular transmission system having a microprocessor-based controller for controlling the operation of a range shift actuator and/or an engine fuel control.
2. Description of the Prior Art
Compound manually shifted mechanical transmissions of the range, splitter and/or combined range/splitter type are in wide use in heavy-duty vehicles and are well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,754,665; 5,272,929; 5,370,013 and 5,390,561, 5,546,823; 5,609,062; 5,642,643 and 5,676,017, the disclosures of which are incorporated herein by reference. Typically, such transmissions include a main section shifted directly or remotely by a manual shift lever and one or more auxiliary sections connected in series therewith. The auxiliary sections most often were shifted by a slave actuator, usually pneumatically, hydraulically, mechanically and/or electrically operated, in response to manual operation of one or more master switches. Shift controls for such systems by be seen by reference to U.S. Pat. Nos. 4,455,883; 4,550,627; 4,899,607; 4,920,815; 4,974,468; 5,000,060; 5,272,931; 5,281,902; 5,222,404 and 5,350,561, the disclosures of which are incorporated herein by reference.
Fully or partially automated transmission systems wherein a microprocessor-based electronic control unit (ECU) receives input signals indicative of various system operating conditions and processes same according to logic rules to issue command output signals to one or more system actuators are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,593,580; 4,595,986; 4,850,236; 5,435,212; 5,582,069; 5,582,558; 5,620,392; 5,651,292 and 5,679,096; 5,682,790; the disclosures of which are incorporated herein by reference.
In range sections utilizing synchronized double-acting clutches, improper range shifting will result in undue wear and/or damage to the synchronizers. If the range section is shifted from range-high to range-low at greater than a reference vehicle speed, or if the main section is engaged prior to the range section in a compound shift, undue wear and/or damage to the synchronizer friction surfaces is likely. These problems, and prior art proposed solutions thereto, may be appreciated by reference to U.S. Pat. Nos. 5,222,404; 5,263,379; 5,199,312 and 5,193,410, the disclosures of which are incorporated herein by reference.
While the prior art systems did protect the range synchronizer by limiting the force at which the range clutch was engaged under certain circumstances, the possible result was unacceptably slow and/or not completed range shifts.